Big Block Cam Timing
07-15-2004, 09:36 AM
#1
Melting Slicks
Thread Starter
Big Block Cam Timing
When would I want to use the 4 degrees advanced or 4 degress retarded (slots on timing gear)? Would TDC be best for everyday applications? 454 is stock with exception of Holley 750, headers, edelbrock manifold and cam package (installing now). Asking the forum since Edelbrock has not responded back yet.
07-15-2004, 09:52 AM
#2
Race Director
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Location: CORVETTE 77 385 C.I. TEXAS
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Advancing & retarding rocks the curve. For example advancing can put more area under the curve.
Depends, you need to state which cam & trans. & rear gears.
Would TDC be best for everyday applications?
07-15-2004, 10:04 AM
#3
Race Director
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I feel the people grinding the cam know better then me what this cam wants so they grind it to be installed straight up. The company supplying the chain set gives you options with their product but I always degree the cam, always for peace of mind and I install them the way the card says.
I do not try to outguess the cam grinder. If they wanted the cam 4 degrees advance they would grind it like that.
I do not try to outguess the cam grinder. If they wanted the cam 4 degrees advance they would grind it like that.
07-15-2004, 10:10 AM
#4
Melting Slicks
Thread Starter
So I need to leave it set for TDC?
The Cam is an Edlebrock 7162.
Specs are: Duration: 300° 306°
Duration @ .50 240° 246°
Cam lift 0.33 0.337
Valve lift 0.56 0.573
Intake open/close 10° BTDC 50° ABDC
Exhaust opn/close 57° BBDC 9° ATDC
Lobe separation 112°
Centerline 110°
Gears are 3.70
The Cam is an Edlebrock 7162.
Specs are: Duration: 300° 306°
Duration @ .50 240° 246°
Cam lift 0.33 0.337
Valve lift 0.56 0.573
Intake open/close 10° BTDC 50° ABDC
Exhaust opn/close 57° BBDC 9° ATDC
Lobe separation 112°
Centerline 110°
Gears are 3.70
07-15-2004, 10:18 AM
#6
Burning Brakes
Member Since: Feb 2004
Location: In the Beautiful Shenandoah Valley of VA
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Most of the various 454 versions were set from the factory at either 8 or 10 degrees BTDC (before top dead center), even the smoggy versions. If you still have the factory emission label present, you can check that. Lars has an excellent paper on CorvetteFaq.com about setting total timing to around 34 or 36 degrees. In the seventies I was running a 396 in my '67 Firebird backed by a Turbo 400. I had a very strong (for the time) Wolverine hydraulic cam and Holley spreadbore carburetor.
I recalibrated the distributor on a distributor machine to limit the total mechanical advance to 7 degrees at the distributor, which is 14 degrees at the crankshaft. All advance was in by about 2300 RPM. I also retained the vacuum advance. For that engine, I set the initial timing spec at the crank to 20 degrees BTDC. It made for ungodly amounts of tire squealing torque. Don't try that on a stock distributor without limiting the mechanical advance though. I also remember it being a bit tough on starters as well; I finally went to a truck starter to keep from busting the snout off the starter.
I would begin around 10 degrees BTDC and work up from there until spark knock made itself known, then back off one or two degrees. Read Lars' paper on timing and changing the distributor advance sprins as well. It's very helpful.
Steve
Whoop. Just realized that you're talking about cam timing, not ignition. Sorry Norval is right, straight up is usually best.
I recalibrated the distributor on a distributor machine to limit the total mechanical advance to 7 degrees at the distributor, which is 14 degrees at the crankshaft. All advance was in by about 2300 RPM. I also retained the vacuum advance. For that engine, I set the initial timing spec at the crank to 20 degrees BTDC. It made for ungodly amounts of tire squealing torque. Don't try that on a stock distributor without limiting the mechanical advance though. I also remember it being a bit tough on starters as well; I finally went to a truck starter to keep from busting the snout off the starter.
I would begin around 10 degrees BTDC and work up from there until spark knock made itself known, then back off one or two degrees. Read Lars' paper on timing and changing the distributor advance sprins as well. It's very helpful.
Steve
Whoop. Just realized that you're talking about cam timing, not ignition. Sorry Norval is right, straight up is usually best.
Last edited by Steve's74; 07-15-2004 at 10:20 AM.
07-15-2004, 11:44 AM
#8
Melting Slicks
Thread Starter
Going to need to do both cam and ignition. Have plans for a 2500-3000 stall as soon as the motor shows me it is running good.
Is there any advantage to the Mallory COmp 9000 electronic over the stock HEI/ I guess should be able to change advance settinig easier with the Mallory?
Is there any advantage to the Mallory COmp 9000 electronic over the stock HEI/ I guess should be able to change advance settinig easier with the Mallory?
